How to create a categorical variable with a specified number of characters?

Question

Cai Chin 2020-12-26

0
链接

此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/702997-how-to-create-a-categorical-variable-with-a-specified-number-of-characters

评论： Stephen23 2020-12-27

Hi, I am trying to create a vector called 'labels' which has 1883 'N's followed by 332 'A's. The code I am currently using just gives a string of N's and A's like this:

NNNNNNNAAAAAAA

However, I wanted to create a variable called 'labels' which has 2215 (2883 + 332) rows and 1 column like this:

[N; N; N; N; .... A; A; A]

Any help would be much appreciated, thanks in advance

% create a categorical variable with 1883 'N's' and 332 'A's'
labels(1:1883) = 'N';
labels(1884:2215) = 'A';

0 个评论
显示 -2更早的评论隐藏 -2更早的评论

请先登录，再进行评论。

请先登录，再回答此问题。

Answer 1

Stephen23 2020-12-26

0
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/702997-how-to-create-a-categorical-variable-with-a-specified-number-of-characters#answer_584797

编辑：Stephen23 2020-12-27

在 MATLAB Online 中打开

labels = [repmat('N',1883,1);repmat('A',332,1)];

or less robustly:

labels(   1:1883,1) = 'N';
labels(1884:2215,1) = 'A';
%               ^^ added

3 个评论
显示 1更早的评论隐藏 1更早的评论

Cai Chin 2020-12-26

Also, when I use the summary function, it gives this error: Check for missing argument or incorrect argument data type in call to function 'summary'. However, I would like it to say:

A 332

N 1883

Stephen23 2020-12-27

在 MATLAB Online 中打开

"however, each letter seems to have an apostrophe before it like this: 'A. How can I resolve this?"

labels = [repmat('N',8,1);repmat('A',3,1)]
labels = 11x1 char array
    'N'
    'N'
    'N'
    'N'
    'N'
    'N'
    'N'
    'N'
    'A'
    'A'
    'A'

The single-quote is simply an artifact of how MATLAB displays character arrays (i.e. it tells us that the data have type char) it is not part of the data itself. If you do not want to display the data within single-quotes then you can write your own display routine based on FPRINTF or similar.

"Also, when I use the summary function, it gives this error: Check for missing argument or incorrect argument data type in call to function 'summary'."

The summary function is not specified to work on character arrays, it is defined to work on table classes, which is why you get that error. My guess is that you actually want something like this:

T = table(categorical(cellstr(labels)));
summary(T)
Variables:

    Var1: 11x1 categorical

        Values:

            A       3    
            N       8    

请先登录，再进行评论。